Methods of Operating a Memory Device Having a Buried Boosting Plate

ABSTRACT

Memory devices are disclosed, such as those that include a semiconductor-on-insulator (SOI) NAND memory array having a boosting plate. The boosting plate may be disposed in an insulator layer of the SOI substrate such that the boosting plate exerts a capacitive coupling effect on a p-well of the memory array. Such a boosting plate may be used to boost the p-well during program and erase operations of the memory array. During a read operation, the boosting plate may be grounded to minimize interaction with p-well. Systems including the memory array and methods of operating the memory array are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/402,300 which was filed on Mar. 11, 2009.

FIELD OF INVENTION

Embodiments of the invention relate generally to memory devices and, inone or more embodiments, more specifically to operation of NAND flashmemory devices.

DESCRIPTION OF RELATED ART

Electronic systems, such as computers, personal organizers, cell phones,portable audio players, etc., typically include one or more memorydevices to provide storage capability for the system. System memory isgenerally provided in the form of one or more integrated circuit chipsand generally includes both random access memory (RAM) and read-onlymemory (ROM). System RAM is typically large and volatile and providesthe system's main memory. Static RAM and Dynamic RAM are commonlyemployed types of random access memory. In contrast, system ROM isgenerally small and includes non-volatile memory for storinginitialization routines and identification information.

One type of non-volatile memory that is of particular use is a flashmemory. A flash memory can be erased and reprogrammed in blocks. Flashmemory is often employed in personal computer systems in order to storethe Basic Input Output System (BIOS) program such that it can be easilyupdated. Flash memory is also employed in portable electronic devices,such as wireless devices, because of the size, durability, and powerrequirements of flash memory implementations. Various types of flashmemory may exist, depending on the arrangement of the individual memorycells and the requirements of the system or device incorporating theflash memory. For example, NAND flash memory is a common implementationof a flash memory device.

A typical flash memory includes a memory array having a large number ofmemory cells arranged in rows and columns. The memory cells aregenerally grouped into blocks such that groups of cells can beprogrammed or erased simultaneously. Each of the memory cells includes afloating gate field-effect transistor or other component capable ofholding a charge. Floating gate memory cells differ from standard MOSFETdesigns in that they include an electrically isolated gate, referred toas the “floating gate,” in addition to the standard control gate. Thefloating gate is generally formed over a channel and separated from thechannel by a gate oxide. The control gate is generally formed over thefloating gate and is separated from the floating gate by another thinoxide layer. A floating gate memory cell stores information by holdingelectrical charge within the floating gate. By adding or removing chargefrom the floating gate, the threshold voltage of the cell changes,thereby defining whether this memory cell is programmed or erased.

The memory array is accessed by a row decoder activating a row of memorycells by selecting an access line, commonly referred to as a wordline,connected to a control gate of a memory cell. In addition, the wordlinesconnected to the control gates of unselected memory cells of a string ofmemory cells are driven to operate the unselected memory cells of eachstring as pass transistors, so that they pass current in a manner thatis unrestricted by their stored data values. Current then flows from thesource line to a data line, such as a column bit line, through each NANDstring via the corresponding select gates, restricted only by theselected memory cells of each string. This places the current-encodeddata values of the row of selected memory cells on the column bit lines.To erase the contents of the memory array, a relatively high voltage isapplied to the memory array such that the source and drain of the memorycells to be erased are forward biased.

Some smaller memory devices may include memory arrays having memorycells formed on a semiconductor (typically silicon)-on-insulator (SOI)substrate. However, as memory devices become smaller and are fabricatedwith smaller die sizes, the proximity of the memory cells of a NANDmemory array may introduce cross-coupling effects between memory cells,such that operations on a memory cell may affect operation of adjacentmemory cells. For example, during a program operation, such an effectmay be referred to as “program disturb.” In such embodiments, attainingthe voltages for a program operation may be difficult withoutintroducing program disturb effects.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram that illustrates a processor-based devicehaving a memory that includes memory devices fabricated in accordancewith one or more embodiments of the present invention;

FIG. 2 is a block diagram that illustrates a memory device having amemory array fabricated in accordance with one or more embodiments ofthe present invention;

FIG. 3 is a cross-section of a portion of the memory array of FIG. 2 inaccordance with an embodiment of the present invention;

FIG. 4 is another cross-section of a portion of the memory array of FIG.2 illustrating a plurality of strings of memory cells in accordance withan embodiment of the present invention;

FIG. 5 depicts a block diagram of the memory array of FIG. 2 and driversthat may be used to operate the memory array in accordance with anembodiment of the present invention;

FIGS. 6A-6D depicts a schematic diagram of a portion of the memory arrayof FIG. 2 and a p-well switch in accordance with an embodiment of thepresent invention;

FIGS. 7A and 7B depict a cross-section of an inhibited string andprogrammed string of the memory array during a first step of a programoperation in accordance with an embodiment of the present invention;

FIGS. 8A and 8B depict a cross-section of an inhibited string andprogrammed string of the memory array during a second step of a programoperation in accordance with an embodiment of the present invention;

FIGS. 9A and 9B depict a cross-section of an inhibited string andprogrammed string of the memory array during a third step of a programoperation in accordance with an embodiment of the present invention; and

FIG. 10 depicts a cross section of a string of the memory array duringan erase operation in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

Turning now to the drawings, and referring initially to FIG. 1, a blockdiagram depicting an embodiment of a processor-based system, generallydesignated by reference numeral 10, is illustrated. The system 10 may beany of a variety of types such as a computer, pager, cellular phone,personal organizer, portable audio player, control circuit, camera, etc.In a typical processor-based device, a processor 12, such as amicroprocessor, controls the processing of system functions and requestsin the system 10. Further, the processor 12 may comprise a plurality ofprocessors that share system control.

The system 10 typically includes a power supply 14. For instance, if thesystem 10 is a portable system, the power supply 14 may advantageouslyinclude permanent batteries, replaceable batteries, and/or rechargeablebatteries. The power supply 14 may also include an AC adapter, so thesystem 10 may be plugged into a wall outlet, for instance. The powersupply 14 may also include a DC adapter such that the system 10 may beplugged into a vehicle cigarette lighter, for instance.

Various other devices may be coupled to the processor 12 depending onthe functions that the system 10 performs. For instance, a userinterface 16 may be coupled to the processor 12. The user interface 16may include buttons, switches, a keyboard, a light pen, a stylus, amouse, and/or a voice recognition system, for instance. A display 18 mayalso be coupled to the processor 12. The display 18 may include an LCD,a CRT, LEDs, and/or an audio display, for example.

Furthermore, an RF sub-system/baseband processor 20 may also be coupledto the processor 12. The RF sub-system/baseband processor 20 may includean antenna that is coupled to an RF receiver and to an RF transmitter(not shown). A communications port 22 may also be coupled to theprocessor 12. The communications port 22 may be adapted to be coupled toone or more peripheral devices 24 such as a modem, a printer, acomputer, or to a network, such as a local area network, remote areanetwork, intranet, or the Internet, for instance.

Because the processor 12 controls the functioning of the system 10 byimplementing software programs, memory is used to enable the processor12 to be efficient. Generally, the memory is coupled to the processor 12to store and facilitate execution of various programs. For instance, theprocessor 12 may be coupled to system memory 26, which may includevolatile memory, such as Dynamic Random Access Memory (DRAM) and/orStatic Random Access Memory (SRAM). The system memory 26 may alsoinclude non-volatile memory, such as read-only memory (ROM), EEPROM,and/or flash memory to be used in conjunction with the volatile memory.As described further below, the system memory 26 may include one or morememory devices, such as flash memory devices, that may include afloating gate memory array fabricated in accordance with embodiments ofthe present invention.

FIG. 2 is a block diagram illustrating a memory device, e.g., NAND flashmemory device 30, which may be included as a portion of the systemmemory 26 of FIG. 1. The flash memory device 30 generally includes anSOI memory array 32. The memory array 32 can include many rows andcolumns of conductive traces logically arranged in a grid pattern toform a number of access lines and data lines. The access lines are usedto access cells in the memory array 32, are usually considered the rowsor “row lines,” and are generally referred to as “wordlines.” The datalines are used to sense (e.g., read) the cells, are usually referred toas the columns or “column lines,” and are generally referred to as “bitlines” or “digit lines.” The size of the memory array 32 (i.e., thenumber of memory cells) will vary depending on the size of the flashmemory device 30.

To access the memory array 32, a row decoder block 34 and a columndecoder block 36 are provided and are configured to receive andtranslate address information from the processor 12 via the address bus38 to access a particular memory cell in the memory array 32. A senseblock, such as sense amplifier block 40 having a plurality of the senseamplifiers, is also provided between the column decoder 36 and thememory array 32 to sense individual data values stored in the memorycells. Further, a row driver block 42 is provided between the rowdecoder block 34 and the memory array 32 to activate a selected wordline in the memory array according to a given row address.

During read and program operations, such as a write operation, data maybe transferred to and from the flash memory device 30 via the data bus44. The coordination of the data and address information may beconducted through a data control circuit block 46. Finally, the flashmemory device 30 may include a control circuit 48 configured to receivecontrol signals from the processor 12 via the control bus 50. Thecontrol circuit 48 is coupled to each of the row decoder block 34, thecolumn decoder block 36, the sense amplifier block 40, the row driverblock 42 and the data control circuit block 46, and is generallyconfigured to coordinate timing and control among the various circuitsin the flash memory device 30.

FIG. 3 depicts a cross-section of a portion of the SOI NAND memory array32 and a buried boosting plate 52, in accordance with an embodiment ofthe present invention. Although the embodiment depicted in FIG. 3includes NAND memory having floating gates, embodiments of the presentinvention may include any other memory cell technology with chargestorage nodes, e.g., charge trap memory, nano-dot memory, etc. Asdiscussed above, the memory array 32 may be fabricated on a wafer thatincludes an SOI portion 54 and a bulk silicon portion 66. The memoryarray 52 includes control gates 56 disposed over a charge storage device(node), e.g., floating gates 58. The floating gates 58 may be separatedfrom the control gates by a dielectric material, such as oxide 60. Thecontrol gates 56 and floating gates 58 are disposed over the silicon 62(which is over the dielectric material that comprises the insulator ofthe SOI portion 54 of the wafer) to form memory cells of the memoryarray 32. The SOI portion 54 may include an insulator layer, e.g., asilicon oxide (SiO2) layer 64 (also referred to as a buried oxide (BOX))disposed over silicon 66. As will be described further, a boosting plate52, may be formed under the insulator (e.g., it may be a conductivelayer buried in the SiO2 layer 64) of the SOI portion 54. The boostingplate 52 may include any conductive material, such as metals, metalalloys, poly Si, etc. In some embodiments, the boosting plate 52 mayinclude tungsten. The boosting plate 52 may be coupled to a boostingplate contact 67 to enable biasing of the boosting plate 52 duringoperation of the memory array 32 and memory device 30.

The memory device 30 may include a transistor array 68, such as fortransferring drive signals to the memory array 32. In one embodiment, asshown in FIG. 3, the transistor array 68 may be disposed on the bulksilicon portion 66, such that the transistor array 68 is not fabricatedon the SOI portion 54. The bulk silicon portion 66 may include anynumber of p-doped regions 70 within n-wells 71 and n-doped regions 72within p-wells 73 to form the desired transistors of the transistorarray 68. The placement of the boosting plate 52 in the SOI portion 54may reduce or eliminate any effect of the boosting plate 52 on theoperation of the transistor array 66. It should be appreciated that anysuitable transistor may be formed as part of the transistor array 68. Insome embodiments, as shown in FIG. 3, the memory device 32 may include ahigh voltage (HV) n-channel MOSFET (NMOS) 74, a HV p-channel NMOS 76, alow voltage (LV) NMOS 78, and an LV CMOS 80.

FIG. 4 is another cross-section of a portion of the memory array 32illustrating a plurality of strings 82 of memory cells 84 in accordancewith an embodiment of the present invention. It should be appreciatedthat each string 82 may include any number of memory cells 84. Asmentioned above, each memory cell 84 may be formed from a control gate56 and a floating gate 58. Each string 82 may include a source selectgate transistor 86 and drain select gate transistor 88. The memory cells84 and select gates 86 and 88 are disposed on a p-well 92 (p-typesilicon) having n-doped regions 94 to form the source and drain regionsfor the memory cells 84 and the select gates 86 and 88. The plurality ofstrings 82 may include a plurality of common source contacts 96 andbitline contacts 98. The p-well 92 and n-doped regions 94 may couple toa bitline 100 for the memory cells 84 through the bitline contacts 98,and a wordline (not shown) may be coupled to each control gate 56.Additionally, the p-well 92 may be biased through the p-well contact102.

As shown in FIG. 4, the boosting plate 52 is disposed in the SOI portion54 such that the boosting plate 52 is disposed under the memory cells 84of the strings 88. Due to the disposition of the boosting plate 52 inthe SOI portion 54 such that the p-well 92 and boosting plate 52 areseparated by the SiO2 layer 64, the boosting plate 52 is in capacitivecontact with the p-well 92. That is, biasing the boosting plate 52 mayexert a capacitive coupling effect on the p-well 92 such that the p-well92 may be influenced by the voltage on the boosting plate 52. Forexample, if the p-well 92 is floating, the p-well may couple up to avoltage if the boosting plate 52 is biased to a voltage. As explainedfurther below, this capacitive coupling effect may be used to affect thep-well 92 during program and erase operations of the memory cells 84. Itshould be appreciated that a boosting plate may be any size, shape, ortopography suitable for achieving the desired capacitive coupling effectwith the p-well 92

FIG. 5 depicts a block diagram of the SOI memory array 32 and driversthat may be used to operate the memory array 32 in accordance with anembodiment of the present invention. The memory array 32 may be coupledto a wordline and select gate driver 104 and a bitline driver 106 tobias the wordlines and bitlines respectively during program, erase,read, and other operations. An array p-well driver 108 may be coupled tothe p-well contact 102, and an array source bias 110 may be coupled tothe common source contacts 96. The boosting plate may be independentlycontrolled through a boosting plate driver 112 coupled to the boostingplate 52 via the boosting plate contact 66.

Turning now to operation of the memory array 32, FIG. 6A depicts aschematic diagram of a portion of the memory array 32 in accordance withan embodiment of the present invention. Additionally, FIGS. 6B-6D depictp-well switching capability of the memory array 32, which may be used toaid operation of the boosting plate 52 in accordance with anotherembodiment of the present invention. As discussed above, the memoryarray 32 may include a plurality of strings 82 comprising a plurality ofmemory cells 84. A string 82 may include any number of memory cells 84to store any number of units of data, such as any number of bits, bytes,etc. The NAND memory array 32 includes local word lines WL(0)-WL(N) andintersecting local bit lines BL(0)-BL(2). A connection 114 to a p-well92 of the strings is shown. As discussed above, a boosting plateconnection 116 is shown coupled to the p-well 92, indicating thecapacitive coupling effect of the boosting plate 52.

The NAND memory array 32 includes the memory cells 84 located at eachintersection of a local word line (WL) and a local bit line (BL). Aswill be appreciated, each memory cell 84 includes a source, a drain, afloating gate, and a control gate. The control gate of each memory cell84 is coupled to (and in at least some cases form) a respective localword line (WL). The memory cells 84 are connected in series, source todrain, to form the NAND string 82 formed between select gates.Specifically, the strings 82 are formed between the local drain selectgates 88 and the source select gate 86. A local drain select line (SGD)is coupled to a respective drain select gate 88. Similarly, the localsource select line (SGS) is coupled to each NAND string 82 through thesource select gate 86. A “column” of the memory array 32 includes a NANDstring 82 and the source select gate 86 and drain select gate 88connected thereto. A “row” of the memory cells 84 are those transistorscommonly coupled to a given local access line, such as a local word line(WL).

As mentioned above and as described further below, during someoperations of the memory array 32, such as a program operation,cross-coupling effects may occur on adjacent memory cells. One suchexample may include a “program disturb” effect between memory cells of aprogrammed string (e.g., a string containing the memory cell or cellsbeing programmed) and memory cells of an inhibited string (e.g., thestring not being programmed). The program disturb effect may bedescribed with reference to FIG. 6 and a programmed string 120 and aninhibited string 122. During program of a memory cell 124, the wordlineWL(1) coupled to the memory cell 124 may be biased to a program voltage(Vpgm). The wordlines WL(0) and other wordlines in the programmed string120 may be biased to a pass voltage Vpass. The bitline BL(0) coupled tothe programmed string 120 may be biased to 0V, and the bitline BL(1)coupled to the inhibited string 122 may be floating or biased to Vcc.During the program, a memory cell 126 that is coupled to the wordlineWL(1) may experience a program disturb, e.g., charge may become trappedin the floating gate of the memory cell 126 from the channel due to thevoltage difference between the channel and the wordline WL(1). Asdescribed further below, during a program, the boosting plate 52 may bebiased to a certain voltage to influence the voltage of the p-well 92(FIG. 4) for both the programmed string 120 and inhibited string 122.

Referring now to FIGS. 6B, 6C, and 6D, the memory array 32 may include ap-well switch 125 coupled to a first p-well P-well(0), a second p-wellP-well(1), and a third p-well P-well(2) in accordance with an embodimentof the present invention. Each p-well P-well(0), P-well(1), andP-well(2) has individual p-well contacts 127 coupled to the p-wellswitch 125. Additionally, the p-well switch 125 includes individualcontacts 129 that each may be coupled to a voltage source, e.g., thep-well driver 108 or a node of the boosting plate 52.

The p-well switch 125 enables each p-well to have individual voltagesduring operation of the memory array 32. During a programming operation,the p-well switch 125 may be “OFF” such that each p-well P-well(0),P-well(1), and P-well(2) are floating. During such a programmingoperation, the individual p-well contacts 127 allow each p-well to haveindividual voltages.

During an erase operation, the p-well switch may be “ON”, allowing thep-wells P-well(0), P-well(1), and P-well(2) to be biased. Similarly,during a read operation, the p-well switch may “ON”, allowing thep-wells to be biased. Thus, during an erase or read operation eachp-well node of P-well(0), P-well(1), and P-well(2) may be biased atcommon voltages through the p-well switch 125. As shown in FIG. 6C, insome embodiments the P-well switch 125 may be formed over the silicon66, similar to transistor array 68. In other embodiments, as shown inFIG. 6D, the p-well switch 125 may be formed over the SOI portion 54 aspart of the memory array 32.

FIGS. 7A and 7B depict a cross-section of the inhibited string 122 andprogrammed string 120 of the memory array 32 during programming of amemory cell in accordance with an embodiment of the present invention.As described above, the memory array 32 is fabricated on the SOI portion54 having the SiO2 layer 64 and silicon 66. FIG. 7A depicts across-section of the inhibited string 122, e.g., those memory cells notbeing programmed and includes a common source contact 128, a bitlinecontact 130, and select gates 132 and 134. FIG. 7B depicts across-section of the programmed string 120, e.g., the string includingthose memory cells being programmed. FIG. 7B includes a common sourcecontact 136, a bitline contact 138, and select gates 140 and 142.

As shown in FIGS. 7A and 7B, in a first step of the programmingoperation, the boosting plate 52 may be biased to about 0V. As shown inFIG. 7A, the bitline coupled to bitline contact 130 of the inhibitedstring 122 is biased to about 2V, and as shown in FIG. 7B, the bitlinecoupled to the bitline contact 138 of the programmed string 120 isbiased to about 0V. The source select gate 132 of the inhibited string122 and the source select gate 140 of the programmed string 120 may bebiased to about 0V via the source gate select line (SGS). The drainselect gates 134 and 142 of the inhibited string 122 and programmedstring 120 may be biased to about 2V via the drain select line (SGD).The p-well 92 is floating and may experience minimal capacitive couplingeffects from the boosting plate 52.

FIGS. 8A and 8B depict a cross-section of the inhibited string 122 andprogrammed string 120 during a second step of the programming operationin accordance with an embodiment of the present invention. As shown inFIGS. 8A and 8B, the boosting plate 52 may be biased to a voltage,Vboost. In one embodiment, Vboost may be about 10V. The bitline coupledto bitline contact 130 and the common source 128 of the inhibited string122 may be floating, enabling the p-well 92 to respond to the biasedboosting plate 52. As discussed above, the capacitive coupling effectbetween the boosting plate 52 and the p-well 92 causes the p-well 92 tocouple up to some voltage less than Vboost. For example, as shown inFIG. 8A, for a Vboost of about 10V, the p-well 92 may couple up to about5V.

The bitline coupled to bitline contact 138 of the programmed string mayremain biased at about 0V. In such an embodiment, biasing of theboosting plate 52 to Vboost may only minimally affect the p-well 92. Forexample, as shown in FIG. 8B, biasing the boosting plate 52 to about 10Vresults in a p-well voltage of about 0.5V in the programmed string 120.

FIGS. 9A and 9B depict a cross-section of the inhibited string 122 andprogrammed string 120 during a third program step in accordance with anoperation of the present invention. To program the memory cell 124 ofthe programmed string 120, the wordline (WL_sel) coupled to the memorycell 124 may be biased to a program voltage, Vpgm, such as about 20V asshown in FIG. 9B. Thus, the memory cell 126 of the inhibited string 122is also experiencing the voltage Vpgm of the wordline (WL_sel). Thewordlines adjacent to the programmed memory cell (WL_unsel) may bebiased to a pass-through voltage (Vpass, also referred as an inhibitedvoltage Vinh), such as 10V, 5V, etc., as shown in FIGS. 9A and 9B.

As clearly seen in FIGS. 9A and 9B, the resulting difference in voltagebetween the p-well 92 of the inhibited string 122 (about 5V) and thep-well 92 of the programmed string 120 (about 0.5V) influences thebehavior of the memory cells 124 and 126 coupled to the selectedwordline. As shown in FIG. 9A, the voltage difference between theselected wordline and the channel on the p-well 92 may be low enough tominimize or eliminate any program disturb. For example, at a Vpgm ofabout 20V on the selected wordline, a p-well voltage of about 5V, andchannel voltage of about 10V, the difference in voltage may minimize oreliminate any flow of charge from the channel into the floating gate ofthe memory cell 126.

As shown in FIG. 9B, the voltage difference between the selectedwordline and the boosted p-well 92 may be large enough to allow normalprogramming of the memory cell 124. For example, the floated p-wellvoltage of the programmed string may about 0.5V, and the selectedwordline may be biased to a Vpgm of about 20V, thus allowing charge fromthe channel to become trapped in the floating gate of the programmedmemory cell 124. In this manner the boosting plate 52 may affect thep-well such that the p-well of both an inhibited string and a programmedstring is optimized to reduce or eliminate program disturb and allowprogramming of any memory cells of the programmed string.

The voltages applied to the lines, p-well, and boosting plate of theprogrammed string and the inhibited string during a program operationaccording to at least one embodiment of this invention are summarizedbelow in Table 1:

TABLE 1 Pgm WL_sel Vpgm WL_unsel Vpass (Vinh) SGS Vsgs SGD Vsgd BL_selVbl_sel BL_unsel Vbl_unsel -> floating Common source Vsource -> floatingP-well Floating Boosting plate Vboost P-well switch OFF

In some embodiments, the boosting plate 52 may be used during an eraseoperation of a block of memory cells of the memory array 32. In aconventional erase operation, the p-well 92 is biased to an erasevoltage Verase, such that charge flows out of the floating gate of theerased memory cells. However, in a conventional erase operation, theremay be some delay associated with biasing the p-well (also referred toas p-well resistive/capacitive (RC) delay). In some embodiments, theboosting plate 52 may be used to reduce this RC delay of the p-well 92and reduce the time for execution of the erase operation.

FIG. 10 depicts a cross section of a string 150 of the memory array 32during an erase in accordance with an embodiment of the presentinvention. As described above, the string 150 is fabricated on the SOIportion 54 having the SiO2 layer 64 and silicon substrate 66. The stringincludes a common source contact 152, a bitline contact 154, selectgates 156 and 158, and memory cells 160.

As shown in FIG. 6, the wordlines of the erased string may be biased toan erase voltage Vwl. The source select gate 156, drain select gate 158,common source coupled to common contact 152 and bitline coupled tobitline contact 154 of the erased string are floating. To reduce RCdelay of the p-well 92 and speed up the erase operation, the boostingplate 52 may be biased to an erase voltage (Verase). As the p-well 92 isalso biased to Verase (such as by turning on the p-well switch 125),biasing the boosting plate before the erase allows the capacitivecoupling effect between the boosting plate 52 and p-well 92 to aidcoupling the p-well 92 to Verase. In other embodiments, the boostingplate 52 may be biased to any suitable voltage to capacitive couple thep-well to the desired erase voltage (Verase), such as about 10V. For anerase of the memory cells 160 of a string of the memory array 32, thevoltages applied to the lines, p-well 92, and boosting plate 52 of theerased string are summarized below in Table 2:

TABLE 2 Erase WL Vwl BL Floating SGS Floating SGD Floating Common sourceFloating P-well Verase Boosting plate 10 V or Verase P-well switch ON

For a read operation of the memory array 32, the boosting plate 52 maybe grounded to eliminate any effect of the boosting plate 52 on thep-well 92. For a read of the memory array 32, the voltages applied tothe lines, p-well, and boosting plate of are summarized below in Table3:

TABLE 3 Read WL_sel Vref WL_unsel Vread SGS Vsgs SGD Vsgd BL_sel Vbl_selBL_unsel 0 V Common source GND P-well GND Boosting plate GND P-wellswitch ON

1. A method of operating a memory device, the memory device comprising acharge-trap memory array, the memory array comprising at least onememory cell, the at least one memory cell being on a semiconductormaterial, the semiconductor material being over a dielectric material,the method comprising: biasing a boosting plate under the dielectricmaterial during an operation of the memory cell.
 2. The method of claim1, wherein the operation comprises programming the memory array and theboosting plate is biased to a boost voltage.
 3. The method of claim 1,wherein the operation comprises erasing the memory array and biasing theboosting plate comprises biasing the boosting plate to an erase voltage.4. The method of claim 1, wherein the operation comprises biasing theboosting plate under the dielectric material during programming, suchthat the boosting plate exerts a capacitive coupling effect on thesemiconductor material.
 5. A method of operating a memory cell on asemiconductor material, the semiconductor material being over adielectric material, the method comprising: biasing a boosting plateunder the dielectric material during the operating of the memory cell,such that the boosting plate exerts a capacitive coupling effect on thesemiconductor material.
 6. The method of claim 5, wherein the operatingcomprises programming the memory cell.
 7. The method of claim 6, whereinprogramming comprises biasing a data line coupled to the memory cell. 8.The method of claim 6, wherein programming comprises biasing an accessline coupled to the memory cell.
 9. The method of claim 6, whereinprogramming comprises floating the semiconductor material.
 10. Themethod of claim 9, wherein floating the semiconductor material comprisesoperating a switch coupled to the semiconductor material such that thesemiconductor material is disconnected to a voltage source.
 11. Themethod of claim 6, comprising biasing the boosting plate such that avoltage differential is created between an access line of the memorycell and the silicon plate.
 12. The method of claim 6, comprising:biasing to about a reference voltage a data line coupled to a string ofcells that includes the cell being programmed, a source select gatecoupled to the string of cells that includes the cell being programmed,a source select gate coupled to a string of cells that are adjacent tothe string of cells that includes the cell being programmed and theboosting plate; biasing the boosting plate to a boost voltage; andbiasing an access line coupled to the memory cell being programmed to aprogram voltage.
 13. The method of claim 6, wherein biasing the boostingplate comprises biasing the boosting plate to increase the voltage ofthe semiconductor material.
 14. The method of claim 6, comprisingfloating a data line of an inhibited string of the memory array.
 15. Themethod of claim 6, comprising floating a common source line of thememory array.
 16. The method of claim 5, wherein operating compriseserasing the memory cell.
 17. A method of claim 16, wherein erasingcomprises biasing a boosting plate under the dielectric material duringthe erasing, such that the boosting plate exerts a capacitive couplingeffect on the semiconductor material.
 18. The method of claim 17,comprising biasing the semiconductor material.
 19. The method of claim18, comprising biasing the boosting plate to a voltage to capacitivelycouple the semiconductor material to a desired erase voltage.
 20. Themethod of claim 19, where the boosting plate and semiconductor materialare coupled to the same voltage and the boosting plate is biased beforethe semiconductor material is biased.
 21. The method of claim 20,comprising floating a data line coupled to the memory cell.
 22. Themethod of claim 20, comprising floating a source select gate, drainselect gate and source coupled to a string including the cell beingerased, and biasing access lines coupled to cells of the string to anaccess line erase voltage.
 23. A method of operating a memory cell on asemiconductor material, the semiconductor material being over adielectric material, the method comprising grounding a boosting platedisposed in the dielectric material over the semiconductor materialduring the operating.
 24. The method of claim 23, wherein operatingcomprises reading the memory cell.